Hypertension in the elderly is associated with impaired glucose metabolism independently of obesity and glucose intolerance.
We evaluated insulin secretion, insulin sensitivity and blood pressure changes after oral administration of glucose in hypertensive and normotensive elderly subjects. The hypertensive group consisted of 12 subjects (aged 72.5 +/- 1.9 years, mean +/- s.e.m.) who had a history of hypertension lasting 10-25 years and were not more than 20% above ideal body weight. The normotensive group consisted of 12 subjects matched to the hypertensive group for age, sex and weight. All subjects underwent an oral glucose tolerance test (75 g glucose dissolved in 300 ml water), an intravenous glucose tolerance test (0.33 g/kg of a 50% glucose solution) and a euglycaemic, moderately hyperinsulinaemic glucose clamp. In both groups, oral glucose tolerance was normal according to the criteria of the National Diabetes Data Group; the hypertensive group showed significantly higher plasma glucose and insulin responses to oral glucose than the normotensive group, suggesting insulin resistance. The results of the euglycaemic clamp confirmed the state of reduced insulin sensitivity. Our data demonstrate that oral but not intravenous glucose produces a fall in blood pressure in hypertensive but not in normotensive patients, probably because activation of the sympathetic nervous system is impaired in hypertensive subjects; moreover, hypertension in the elderly seems associated with a state of reduced sensitivity to insulin.